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Wright <br /> Environmental <br /> March 2, 2004 Services, Inc. <br /> Construction • Engineering ♦ Remediation <br /> San Joaquin County 5 2004 <br /> Public Health Services MAR 0 <br /> Environmental Health Department ENV1kuNN1E'd'I HEALTH <br /> 304 E. Webber Ave., Third floor PERMIT/SERVICES <br /> Stockton, CA 95202 <br /> ATTN: Mr. Mike Infurna, <br /> Re: Cox & Cox,595 E. 11" Street,Tracy,CA 95736,EI1D Site Code 1933 <br /> Amendment to Approved Work Plan for Corrective Action,MW-3 and MW-9 <br /> Dear Mr. Infurna, <br /> Wright Environmental Services, Inc. (Wright) has prepared this amendment to the <br /> previously approved work plan and requests the San Joaquin County Environmental <br /> Health Department (EHD) approve this amendment that follows changes implemented as <br /> a result of conditions discovered during the course of work and as a formality following <br /> conversations between EHD and Wright staff. Wright submits this request on behalf of <br /> Cox and Cox (responsible party) for the above referenced site: <br /> Summary <br /> The EHD reviewed the CAP dated March 27, 2003, commented on May 01, 2003 and <br /> later approved a work plan for limited excavation around MW-3 and MW-9 dated <br /> October 10, 2003. That approved work plan described a corrective action that was <br /> intended to address the EHD requirement to evaluate and enact the most cost-effective <br /> and feasible corrective action since Total Petroleum Hydrocarbons as Gasoline (TPHG) <br /> were at the highest in groundwater and free product present in MW-3 and MW-9. <br /> Based upon observations during implementation of the corrective action work, Wright <br /> attributes this rise to residual TPHG located in capillary fringe and upper portions of the <br /> aquifer in and around monitoring wells that were just down gradient from the former tank <br /> pit and located between two large subsurface utilities that somewhat confined lateral <br /> movement and apparently offer preferential pathways between and along those confining <br /> structures and the two destroyed monitoring wells. <br /> The structures within the trailer park, two large utilities that are interpreted to somewhat <br /> confine the lateral movement of contaminants and the accessibility of contaminated soils <br /> between those utilities, and the location of the stable dissolved plume underlying these <br /> structures led Wright to conclude that excavation of accessible contaminated soils from <br /> around MW-3 and MW-9 was and continues to be the most cost effective and feasible <br /> corrective action. possibility an "in-situ" process using native biologic microbes and <br /> enhanced application and distribution methods would limit subsurface disturbance and <br /> improve remediation efficacy by reaching residuals interpreted to arise in the vadose zone <br /> and upper portions of the aquifer near these monitoring wells. <br /> 67 E. 10th Street • Tracy,CA 95376 <br /> 209.833.0758 . Fax 209.832.5152 <br /> wright@inreach.com Lic. #651501 A-R Ha Mat, C21 <br /> websit http;//wrightenvironmentalse"ices.com Page I <br />